1. Field
Embodiments of the present invention relate to an electric disk brake, and more particularly, to an electric disk brake that is easily capable of easily controlling an actuator when a parking brake force is released from the electric disk brake and of preventing damage of components caused by releasing an excessive parking brake force.
2. Description of the Related Art
Disk brakes are devices that forcibly compress a frictional pad on both sides of a rotating disk together with wheels of a vehicle so that rotation of the disk is stopped, thereby braking the vehicle. These disk brakes include parking brakes that electrically operate during parking and maintain the vehicle in a stopped state.
In general, an electric disk brake includes a pair of pad plates that are disposed on both sides of a disk and generate a brake force by compressing the disk, a carrier that supports the pair of pad plates, a caliper housing that is slidably installed in the carrier so as to press the pair of pad plates and has a piston moved by a brake hydraulic pressure, and an actuator that operates the piston using a mechanical mechanism.
Such an electric disk brake includes a so-called ball in ramp (BIR) type electric disk brake including a fixed ramp plate fixedly installed in the caliper housing, a rotating ramp plate that rotates by an operation of a parking cable, balls that are installed between the fixed ramp plate and the rotating ramp plate and make a forward movement of the rotating ramp plate when the rotating ramp plate is rotated, a push rod that is disposed adjacent to the rotating ramp plate and pushes the piston, an adjuster screw-coupled to the push rod, and a spring that restores the push rod to its original position.
The BIR type electric disk brake is generally referred to as a BIR caliper type and is disclosed in U.S. Patent Publication No. 2012/029214 and Korean Patent Publication No. 10-2013-0034605. According to the disclosure, the BIR type electric disk brake is configured in such a way that, as a rotation force generated by a motor of an actuator is transferred to the rotating ramp plate of a ramp unit using a decelerator (gear assembly), a rotation motion is converted into a rectilinear motion and pushes the push rod, and the push rod pushes the piston together with the adjuster so that a frictional pad can closely contact the disk and a parking brake force can be generated.
In this case, the rotating ramp plate is directly connected to a final output gear among gears of the decelerator, receives the rotation force, and is rotated in a direction in which the parking brake force is applied to the rotating ramp plate, or is rotated in a direction in which the parking brake force is released from the rotating ramp plate.
However, when an excessive rotation force is transferred to the rotating ramp plate when the parking brake force is released, the balls may escape from the ramp unit, or an excessive load may be applied to internal components so that the internal components may be damaged.